Global Monitoring Annual Conference

As climates change, the lush tropical ecosystems of the Amazon Basin may release more of the greenhouse gas carbon dioxide into the atmosphere than they absorb, according to a new study published Feb. 6 in Nature that included ESRL GMD authorship.
An international team of scientists found that the amount of yearly rainfall was the driving factor behind the amount of carbon dioxide (CO2) taken up and released from Amazonia in 2010 and 2011. During a wet year, the Amazon forests were roughly carbon-neutral: Forests "inhaled" more carbon dioxide than they "exhaled,” but biomass burning, which releases carbon dioxide, compensated for the difference. In contrast, during a very dry year forest growth and carbon uptake stalled and biomass burning increased, resulting in the region "exhaling” substantial amounts of carbon dioxide to the atmosphere.

Background: Previous estimates of Amazon Basin carbon uptake and release have been based on either numerical models or small time- and space-scale measurements. The measurements in this study are from light aircraft that are representative of most of the Amazon Basin and span two full years.

Significance: The relationships, and feedbacks, between the carbon cycle and climate are a first-order uncertainty in climate projection. The Amazon Basin, at nearly the size of the lower 48 states and containing a large fraction of Earth’s living biomass, is a critically important region for understanding these feedbacks.